The present invention relates to a device and method for allowing and/or improving the injection of fuel assisted by compressed air or gas, or pneumatic injection, into an internal combustion engine and is applicable to a four or two stroke engine and more particularly to an internal combustion engine with air scavenging.
In the particular case of a two stroke engine with crank case scavenging during a considerable part of the air and fuel intake cycle, the transfer and exhaust ports are simultaneously opened and a part of the air-fuel mixture admitted escapes to the atmosphere before the exhaust ports are closed, thereby resulting in a considerable reduction in an operating efficiency of the internal combustion engine and considerable discharge of pollutants.
To avoid the disadvantages encountered in the prior art, French Pat. No. FR 490.166 proposes a scavenging of the cylinder solely with air coming from the pump crank case, with another part of the air from the pump crank case being fed at near maximum pressure reached in this housing, into a sealed chamber which serves as compressed air source for supplying the pneumatic fuel injection device.
It has been discovered that such a device operated better when it was fed with compressed air at a pressure higher than that existing in the pump crank case.
The prior art may also be illustrated by, for example British Pat. No. GB-A-572.080, German Pat. No DE-C-833.855, U.S. Pat. No. 3,190,270, and French Pat. No. FR-A-2 292 111.
The device of the invention uses the pressure wave effect reigning in the exhaust pipes for enhancing the pneumatic injection. The result is a better quality of pneumatic injection, an increased filling of the engine with air, an increase in the amount of residual combusted gases resulting in a reduction of Nox discharges, partial recovery of the fuel short circuited to the exhaust and a possible reduction of noise due to the exhaust pressure wave effects.
Thus, the present invention relates to an internal combustion engine comprising a means for pneumatically injecting fuel and an system for an internal combustion engine. In accordance with the present invention, the internal combustion engine includes an auxiliary duct having a first end or opening which is connected to an exhaust pipe of the exhaust system and a second end or opening connected to the injection means.
The internal combustion engine includes a pump crankcase, a chamber connecting the pump crankcase to the fuel injection means, which chamber forms an injection chamber, and an auxiliary duct connecting the exhaust pipe of the exhaust system to the injection chamber, which injection chamber may include an obstruction means such as, for example, a stop or check valve, with the obstruction means being located prior to a connection of the auxiliary duct to the injection chamber.
The auxiliary duct may include an obstruction member such as, for example, a stop or check valve adapted to intermittently open under an effect of a mechanical means such as, for example, a cam, or by pneumatic control or electromagnetic control.
It is also possible in accordance with the present invention for the auxiliary duct to include a third aperture opening into a gas source and an obstruction means placed in the aperture, with the obstruction means taking the form of a stop or check valve. Preferably, an end of the auxiliary duct connected to the exhaust pipe is positioned in the exhaust pipe at a location where the pressure wave is maximum, and has a convergent shape with a cross section decreasing from the exhaust pipe toward the auxiliary duct.
The present invention may be applied to an engine comprising at least two cylinders each of which comprises an exhaust pipe and an injection member. In this case, the engine may also comprise at least one crossed auxiliary duct connecting said exhaust pipe of one of the cylinders to the injection member of the other cylinder.
The present invention may be applied to an engine comprising at least two cylinders each of which comprises an exhaust pipe, an injection member and an injection chamber connected to said injection member of one the cylinders, or cylinder considered. In this case, the engine may also comprise at least one crossed auxiliary duct connecting said injection chamber to the exhaust pipe of the other cylinder.
If it is the cylinder considered which comprises a pump crank case, the engine may comprise at least one injection chamber connecting the pump crank case to the injection member of the cylinder considered and the crossed auxiliary duct may connect the exhaust pipe of the other cylinder to the injection chamber of the cylinder considered.
The present invention may also be applied to an engine comprising at least two cylinders, with each of the cylinders having an exhaust pipe and an injection means. In this case, the engine may also comprise at least two auxiliary crossed ducts, each of them connecting the exhaust pipe of one of the cylinders to the injection means of the other cylinder.
The present invention may also be applied to an engine comprising several cylinders at least one of which comprising an exhaust pipe and another comprising a pneumatic injection member. In this case an auxiliary duct may connect the exhaust pipe to the pneumatic injection member.
If this engine is an engine whose cylinders comprise a pump crank case, it may also comprise at least two injection chambers, each of them connecting the pump crank case of one of the cylinders, or cylinder considered, to the injection means of the same cylinder and each of the auxiliary ducts may connect the exhaust pipe of the other cylinder to the injection chamber connected to the injection means of the cylinder considered.
The present invention may be applied to an engine comprising at least two cylinders, one at least of which comprises a pump crank case. In this case, the engine may comprise at least one so called cross injection chamber connecting said pump crank case to the injection member of the other cylinder.
Still within the scope of the present invention, this other cylinder may comprise an exhaust pipe and an auxiliary duct which connects the exhaust pipe of this other cylinder to the crossed injection chamber connected to the injection member of this same cylinder.
The present invention may be applied to an engine having at least two cylinders each equipped with a pump crank case. In this case the engine may comprise at least two crossed injection chambers, each of them connecting the pump crank case of one the cylinders to the injection member of the other cylinder.
Still within the scope of the present invention, the engine may comprise at least two auxiliary ducts, each of them connecting the exhaust pipe of one of the cylinders or cylinder considered, to the injection chamber connected to the injection means of this same cylinder.
Thus it is apparent that, in the case of multi-cylinders, the present invention provides numerous combinations of communications between the exhaust pipes of the different cylinders and the injection means, as well as between the pump crank cases and the injection members.
Similar combinations are also possible within the scope of the present invention, more especially when the engine comprises an exhaust manifold or if it comprises a common injection chamber communicating with several pump crank cases and at least one injection member. For example, still within the scope of the present invention, an auxiliary duct may be connected to an injection means via the common injection chamber, or not.
The injection chamber may be formed by a duct, this is moreover the preferred embodiment.
The present invention also provides a method for providing fuel injection in an internal combustion engine equipped with a pneumatic injection means and an exhaust pipe wherein a communication is formed between the exaust duct and the injection means. This method may be applied to an engine comprising a pump housing or crank case. In this embodiment part of the compressed gases coming from the pump housing is directed towards the injection means and is combined with the gases coming from the communication between the exhaust and the injection means.
Still within the scope of the present invention, the communication may be placed in relation with a gas source via an obstruction means such as a stop valve or non return valve.
When the engine to which the method of the invention applies comprises at least two cylinders each of which comprises an exhaust pipe and an injection means, at least one so called crossed communication may be provided connecting the exhaust pipe of one of the cylinders or cylinder considered to the injection means of the other cylinder.
If the method of the invention is applied to an engine in which of said cylinders comprises a pump crank case and a transfer duct, a part of the compressed gases coming from the pump crank case of the cylinder considered may be directed towards the injection member of the same cylinder and be combined with the gases coming from the communication between the exhaust pipe of the other cylinder with the injection member of the cylinder considered.
If the method of the invention is applied to an engine comprising at least two cylinders, at least one of these cylinders comprising a pump crank case, a part of the compressed gases coming from the pump crank cases may be directed towards the injection member of another cylinder.
When the method of the invention is applied to an engine in which each cylinder comprises an exhaust pipe, the communication may connect the exhaust pipe of this other cylinder to the injection means of this same cylinder and at least a part of the compressed gases coming from the pump crank case may be directed towards the injection member and be combined with the gases coming from the communication.